Adverse Effects

Definition and examples

Any pharmacologically active drug can also cause adverse drug reactions (ADRs). According to the WHO definition, these are harmful and unintended effects during intended use. In English, this is referred to as an (ADR). Typical adverse effects are:

  • Headache, dizziness, sleep disturbance, fatigue, impaired reaction time.
  • Gastrointestinal symptoms such as nausea, diarrhea, constipation.
  • Skin rashes
  • Local reactions, for example on the eye, ear, skin.
  • Pain
  • Allergic reactions

Side effects describe in a narrow sense unintended effects of the drug, which are related to its pharmacological properties. However, the term is also used in common parlance and in this text as a synonym for adverse drug reactions. Patients must be aware of the risks before use and be informed accordingly.

Information on adverse effects

The information on possible adverse effects can be found in the drug information leaflet and in the package leaflet. On the one hand, they originate from placebo-controlled clinical studies and, on the other hand, from market surveillance after marketing authorization (spontaneous reports, ). Rarely, adverse effects may occur that were previously unknown. It is essential that they are reported to the regulatory authorities by the experts. This is also referred to as pharmacovigilance. Various drugs have had to be withdrawn from the market after they were approved because new undesirable effects were discovered. One example is the painkiller rofecoxib (Vioxx), which causes cardiovascular disease. Market surveillance is especially – but not exclusively – important for new drugs because rare side effects are not discovered in clinical trials due to the limited number of participants. The question of causality always arises, i.e. whether the drug can actually be held responsible. Adverse effects can be observed during or after treatment, but never before treatment.

Causes

A common cause of adverse effects is a lack of selectivity of the active ingredients. Thus, they interact not only with the intended drug target but also with other structures, tissues, and targets in the body. Perfect selectivity is almost impossible to achieve because of the large number of possible targets. Many adverse effects are predictable and dose-dependent and are derived from the pharmacological properties of the drugs. For example, antihypertensive drugs may reduce blood pressure too much and cause symptoms such as dizziness or palpitations. Insulins can cause hypoglycemia (low blood sugar) and anticoagulants can cause bleeding. In addition, however, unpredictable disturbances exist that are mediated by the immune system, among other factors.

Severity

Adverse effects vary in severity. They can be harmless (e.g., mild skin redness) to life-threatening. Severe adverse reactions include organ failure, severe skin reactions, respiratory failure, anaphylaxis, agranulocytosis, myocardial infarction, malformations, hypotension, gastric hemorrhage, and cancer. Serious adverse effects are life-threatening, can lead to hospitalization, and can leave permanent damage.

Frequency

Adverse effects are listed by organ class (MedDRA) and by frequency:

  • Very common: > 10%
  • Frequent: 1% – 10%
  • Occasional: 0.1% – 1%
  • Rare: 0.01% – 0.1%
  • Very rare: < 0.01%

Desirable side effects

Side effects are not necessarily undesirable. For example, it is known that 1st generation antihistamines can make you tired. Some antihistamines are therefore also used as sleep aids.

Prevention

Some adverse effects are preventable. Tetracyclines can make the skin sensitive to the sun’s rays. Severe sunburn can be prevented with good sun protection and avoidance of intense radiation. Possible measures:

  • Start with low dose (creep in), gradually discontinue (creep out).
  • Administering medications that have been tolerated in the past.
  • Taking with food
  • Sufficient clarification before initiating drug therapy.
  • Discussion with a medical professional
  • Observance of the precautions in the professional information
  • Sufficient information to patients
  • Use drugs with a good safety profile
  • Avoid drug-drug interactions